1. Field of Invention
The invention provides an improved process for the large scale production of [R-(R*,R*)]-5-(3-chlorophenyl-3-[2-(3,4-dihydroxyphenyl)-1-methylethyl] -2-oxazolidinone which is an intermediate useful in making compounds that have antidiabetic and/or antihyperglycemic and/or antiobesity properties in mammals and has the structural formula: ##STR1##
2. Description of the Prior Art
As described in copending application Ser. No. 164,524, filed Dec. 9, 1993 a process improvement for the preparation of [R-(R*,R*)]-5-(3-chlorophenyl-3-[2-(3,4-dihydroxyphenyl)-1-methylethyl]2-o xazolidinone which results in higher yields and purity as well as the elimination of a separate purification procedure is described which gives the desired product in a 75% overall yield and a purity of 80-90%.
U.S. Pat. No. 5,061,727 and copending application Ser. No. 164,524 do not teach the process of preparing [R-(R*,R*)]-5-(3-chlorophenyl-3-[2-(3,4-dihydroxyphenyl)-1-methylethyl]-2- oxazolidinone by the addition of a solution of [R-(R*,R*)]-5-(3-chlorophenyl-3-[2-(3,4-dimethoxyphenyl)-1-methylethyl]-2- oxazolidinone in methylene chloride to methylene chloride while simultaneously adding boron tribromide.